5) (20 pts) Figure below shows a tank of cross-sectional area A that initially (t=0) contains two layers, each of depth H: oil (density o ), and water (). A sharp-edged orifice of cross-sectional area a and the coefficient of contraction 0.62 in the base of the tank is then opened. Derive an expression for the time t taken for the water to drain from the tank, in terms of H,g,A,a,0, and w. Neglect friction and assume that Aa